owner-csound-outgoing wrote
>From owner-csound-outgoing Thu Oct  2 14:54:11 1997
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Date: Thu, 2 Oct 97 14:54:11 GMT
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To: owner-csound-outgoing
Subject: BOUNCE Csound: Non-member submission from [Erik Spjut ]

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Date: Thu, 02 Oct 1997 07:55:33 -0700
From: Erik Spjut 
Subject: Re: feed back loops
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To: charlie hubbard , csound 
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At 4:20 PM -0500 9/30/97, charlie hubbard wrote:
>Can someone give me an example of a feedback loop?
>Is that possible in csound or do you have to synthesize
>a feedback loop like that?

Feedback loops are possible in Csound but you have to set kr=sr to make
them work. Short ones (of one or two samples) are relatively easy. Long
ones (like 0.5 seconds) are well nigh impossible. Russel Pinkston has
several examples in his orc's. A short example (with two 1-sample feedback
loops) follows:

sr     = 44100
kr     = 44100 ;permit access to aprev's
ksmps  = 1
nchnls = 1
;-------------------------------------------
        instr 10;IIR Filter Example (thanks to Russell Pinkston)
a1      linseg  0, 0.01, 10000, p3-0.1,9000,0.09,0,1,0
a2      oscil   a1,p4, 1 ;Generate an input
aprev1  init    0                       ; init y(n-1) to 0
aprev2  init    0                       ; init y(n-2) to 0
ainput   =      a2
;              y(n) = a0x(n) - b1y(n-1) - b2y(n-2)
aoutput =       1*ainput - 0.5*aprev1 - 0.5*aprev2
aprev2  =       aprev1
aprev1  =       aoutput
        out     aoutput
        endin

-------------------------------------------------------------------------------
Erik Spjut (rhymes with cute) - Acting Director,The Center for Design Education
and/or Associate Professor of Engineering
Harvey Mudd College, Claremont, CA 91711  USA
Erik_Spjut@hmc.edu      Ph & Voice mail (909) 607-3890      Fax (909) 621-8967



-- 
James Andrews, maths CDO, ext.3977